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Monday, 18 August 2014

Are Dodder Plants (Cuscuta) The Future Tool For Gene Transfer?

Scientists from Virginia Tech and Pennsylvania State University have discovered a potentially new form of plant communication, one that allows them to share an extraordinary amount of genetic information with one another.

Jim Westwood, a professor of plant pathology, physiology, and weed science in the College of Agriculture and Life Sciences, throws open the door to a new arena of science that explores how plants communicate with each other on a molecular level. It also gives scientists new insight into ways to fight parasitic weeds that wreak havoc on food crops in some of the poorest parts of the world.

“The discovery of this novel form of inter-organism communication shows that this is happening a lot more than any one has previously realized,” said Westwood. “Now that we have found that they are sharing all this information, the next question is, ‘What exactly are they telling each other?’.”

Cuscta pentagona | Image: James Westwood

Westwood and his team examined the relationship between a parasitic plant, dodder,
and two host plants, Arabidopsis and tomatoes. In order to suck the
moisture and nutrients out the host plants, dodder uses an appendage
called a haustorium to penetrate the plant. They previously broke
new ground when he found that during this parasitic interaction, there
is a transport of RNA between the two species. RNA translates
information passed down from DNA, which is an organism’s blueprint.

This new work of Westwood and his team expands the scope of this exchange and examines the
mRNA, or messenger RNA, which sends messages within cells telling them
which actions to take, such as which proteins to code. It was thought
that mRNA was very fragile and short-lived, so transferring it between
species was unimaginable.

But they found that during this parasitic relationship, thousands
upon thousands of mRNA molecules were being exchanged between both
plants, creating this open dialogue between the species that allows them
to freely communicate.

Through this exchange, the parasitic plants may be dictating what the
host plant should do, such as lowering its defenses so that the
parasitic plant can more easily attack it. Westwood’s next project is
aimed at finding out exactly what the mRNA are saying. His work is
sponsored by the National Science Foundation.

Using this new found information, scientists can now examine if other
organisms such a bacteria and fungi also exchange information in a
similar fashion.

These findings could also help solve issues of food
scarcity. “Parasitic plants such as witchweed and broomrape are serious
problems for legumes and other crops that help feed some of the poorest
regions in Africa and elsewhere,” said Julie Scholes, a professor at the
University of Sheffield, U.K., who is familiar with Westwood’s work but
was not part of this project. “In addition to shedding new light on
host-parasite communication, Westwood’s findings have exciting
implications for the design of novel control strategies based on
disrupting the mRNA information that the parasite uses to reprogram the
host."

Westwood said that while his finding is fascinating, how this is applied will be equally as interesting. “The beauty of this discovery is that this mRNA could be the
Achilles heel for parasites,” Westwood said. “This is all really
exciting because there are so many potential implications surrounding
this new information.”

"Because RNA normally functions within an individual cell, we generally think that we keep our RNAs to ourselves.Westwood and his team now show that the parasitic dodder plant breaks that rule. When dodder
attacks a host plant, it opens up a conduit through
which messenger and perhaps other regulatory
RNAs are exchanged between parasite and host. Because a single dodder
plant can
attack multiple hosts, such exchanges may
underlie instances of genes transferring between species." writes the editor of Science as part of editorial summary for this article.